Apparatus for transmitting changes in gauge conditions



Q Dct, 1i, 194-9 H D GIFFEN 2,484,218

APPARATUS FO R T RANSMIT'I'ING CHANGES IN GAUGE CONDITIONS Filed May 13, 1944 4 Sheets-Sheet 1 5 m E 2 Q 1170672701. jfczroeyfl Gflen Gct. M, 19499 2,484,218

GlFFEN APPARATUS FOR TRANSMITTING CHANGES IN GAUGE CONDITIONS Filed May 15, 1944 4 Sheets-Sheet 2 AMPLIFIER l N VEN TOR.

@j/a/We em Oct 11, 1949. H. D. GIFFEN APPARATUS FOR TRANSMITTING CHANGES IN GAUGE CONDITIONS Filed May 13, 1944 4 Sheets-Sheet 3 vi a I AJNJflOJA/J MAJ/$739381 ---c 4,006. a 0a m 0d. 11, 1949. H. D. GIFFEN 2,434,218

mrmmwus FOR TRANSMITTING cmmems IN GAUGE CONDITIONS 4 Sheets-Sheet 4 Filed May 15, 1944 fi /j 12576 fllllll VIII" Patented a. 11, 1949 APPARATUS FOR TRANSMITTING CHANGES IN GAUGE CONDITIONS Harvey D. Giffen,

El Caion, CaliL, assignor to Consolidated Vultee Aircraft Corporation,

San

Diego, Calif., 'a corporation of Delaware Application May 13, 1944, Serial No. 535,481

Claims.

This invention relates to the transmission of signals indicative of changes which occur in difierent parts of a movable device, as, for example, an aeroplane, while it is undergoing such changes at rapid rates. This application is a continuation in part of my prior application Serial No. 458,224, filed September 14, 1942, and now abandoned.

The general object of the invention is to pro vide a new and improved apparatus for producing signals representing such changes.

Another object is to provide a new and improved apparatus for producing signals indicative of flight and stress data of aeroplanes in flight, such as airspeed, acceleration, strain measurements, control angles, etc., with a high degree of accuracy.

Another object is to provide an apparatus for producing signals indicating changes in a plurality of detector devices or gauges by making separate signals for each gauge in such rapid sequence and by repeating such sequence signals at extremely short intervals of time so as to produce a substantially continuous series of signals which can then be analyzed to give a separate and substantially continuous record of the changes in each gauge.

Another object is to provide an apparatus for producing signals indicative of changes in gauges and utilizing a beat frequency oscillator, one component of which is caused to vary in pitch according to the stimuli being studied and providing an audio frequency signal suitable for transmission to a remote point.

Other objects and advantages will become readily apparent from the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a perspective view of an aeroplane in flight equipped with the mobile part of a preferred form of the invention.

Figure 2 is a diagrammatic illustration of the ground part of the same form of the invention.

Figure 3 is a wiring .diagram of the mobile part of the apparatus. 1

Figures 4 to 14, inclusive, are diagrammatic representations of the wave forms and variations in different parts of the apparatus.

Figures to 20, inclusive, illustrate types of gauge devices that may be used in the apparatus.

While the invention is susceptible of embodiment in many different forms, I have shown in the drawings and shall herein describe in detail one embodiment, with the understanding that the present disclosure is to be considered as an 2 exemplification of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

In the form of apparatus selected for purposes of illustration the invention is adapted to transmit in rapid sequence signals modulated by gauge devices located on various parts of an aeroplane. In Figure 1 there is illustrated an aeroplane 2!! in flight. It is equipped with an antenna 2i and a radio transmitter 35. Gauge devices 23 to 3d are located on various parts of the aeroplane so as to be actuated individually by the parts or accessories with which they are associated. The radio transmitter may be the transmitter otherwise used for communication purposes. 38 indicates the major part of the mobile portion of the invention, and 3'? indicates generally the leads or connecting wires running from the gauge devices to the part 35.

The ground part of the apparatus as illustrated in Figure 2 comprises an antenna 40, a receiver at of modulated audio frequency signals, an amplifier ii and a recorder .53. The receiver, amplifier and recorder may be of more or less standard design. The recorder is herein shown as of the type which records the audio frequency signals on a film so that the film may be used conveniently with the type of analyzer disclosed in a co-pending application of Harvey D. Gifien, Serial No. 478,367, filed March 8, 1943, now Patent No. 2,380,231 dated July 10, 1945, and entitled Method of and apparatus for analyzing recorded data.

It is contemplated that other forms of recorders may be used, as, for example, those printing on a tape, etc. A monitor consisting of a speaker is is preferably connected to the receiver M for obtaining an audible signal for test or other purposes.

The exemplary form of the invention will now be described in more detail with reference to Figure 3.

Of the gauges indicated in Figure 1, numbers 24, 25 and it are shown in Figure 3. These gauges (and the others as well) are preferably of a resistance or reluctance type that can be connected in as two arms of a Wheatstone bridge at. Thus the gauges have elements 5i and 52 connected together at 53. The common points of all of the gauges are connected together, and by a lead it are connected to one end of a coupling coil 55, the other end of which is connected by a lead 56 to the common mid-point while the leads from a motor 66 ,bodying an oscillator tube 19.

, frequency from determined as a function of the duration of,

be transmitted. In this connection, the

s gnals to that at least generator frequency should be such one complete frequency cycle of the generatorv will occur within the duration of the shortest signal impulse to be transmitted. The upper frequency limit is determined in accordance with various electrical facto such as radiation characteristic, high frequency resistance of con-.

ductors, and the like; and the upper frequency limit may range anywhere from 4,000 to upwardly of 50,000 cycles per second. In practice,

' an optimum frequency of 1,000 cycles per second has been found to be adequate for practical purposes.

The gauge devices are arranged to be connected, one at a time and in rapidly recurring sequence, as arms of the bridge circuit, by means of the leads 31, leads 60 and a switch'mechanism 6!. This switch mechanism is illustrated in Figure 3 as comprising a pairof rotating contact arms 62 and 63, the outer ends of which pass over and engage successively contacts 64 and 65 arranged annularly around the axes of rotation of the switch arms. The leads 31 from one end of each gauge are connected to the contacts 50 the other end of each gauge are connected to the contacts 65. By rotating the arms in synchronism the gauges are connected individually and in predetermined sequence into the bridge circuit.

Normally, the arms of the switch mechanism are rotated synchronously at a constant rate by and suitable gearing '51 and 68, so that each gauge is connected in the bridge circuit with predetermined frequency, the length of time each switch device is closed being determined the arcuate width of the rotating arms and in part by the speed of rotation of the arms.

,The number of switch contacts can be varied in accordance with the number of gauges it is desired shall be used, twenty-two being shown in Figure 3. With that number of contacts the switch arms are preferably of approximately four'revolutions per second, so each contact has a duration on the order of $40 second.

A coil 10 is coupled to coil 55 and arranged to conduct the A. 0. bridge carrier current from the generator 59, as modulated by successive gauges, to an amplifier indicated generally as H, after which the amplified current is rectified in an electronic rectifier 12 and filtered in a filter 13. A lead 14 extends from the filter to ground, and a lead 15 is connected to injector grids of a pair of reactance tubes 16 and 11, one of which (18) acts as a variable capacity and the other (11) as a variable inductance in a variable oscillator circuit 18 cm- A lead 80 feeds the variable frequency from the oscillator 18 into a mixer tube 8| to which there is also fed a fixed a crystal controlled oscillator 82, by a lead 83. Thevariable frequency from the oscillator 18 and the fixed frequency from the oscillator 82 act to form a beat note of a frequency proportionate to the frequency change in In a preferred form of the invention the fixed frequency oscillator 82 was tuned at 4.000.000 cycles and the oscillator 18 is also tuned 4 at 4,000,000, cycles when the bridge 50 is balanced,

. and 4,005,000 cycles beat frequency of 5,000 cycles. Thus as a gauge varies it produces a frequency at 84, which varies between zero and 5,000 cyclesin proportion to the magnitude of the stress or stimuli acting upon the ge.

Tubes 18 and 11 are arranged in such a way that the oscillations of circuit 18 are fed back to the No. 1 grid of each tube by connections 90, 9|. Thus grid 11' of tube 11 is fed through a small condenser 11 and grid 16' of tube 16 through resistors 16 and 16 Condenser 18 is a blocking condenser to remove D. C. from the grid. This constitutes a phasing control of the oscillator circuit, which, in turn, is capacities of the tubes.

' by the radio transmitter 35 on the aeroplane, or

by other suitable means, to a receiving and recording means such as that shown in Figure 2.

A power source 05 is provided for the filaments of the tubes, and a power source 96 to provide positive high voltage for the tubes.

In Figures 4 to 14 are illustrated the wave forms of the different potentials or frequencies which exist in the different parts of the circuit of the the invention. As mentioned herelnbefore, the part 50 is fundamentally an A. C. bridge. The bridge carrier as supplied by the generator 59 is illustrated in Figure 4. The modulation by a gauge responding to a maximum stress Figure 5, and the modulated Figure 6. Figure 7 shows the modulated bridge carrier after amplification in amplifier 1i, preferably to a relatively high potential such as '50 volts, and Figure 8 the wave form after rectification at 12 and filtering at 13. The varying potential of Figure 8 is fed to the reactas shown by the curve of Figure 9. The frequency of oscillator 18 with'the ,bridge 50 in balance, which is therein taken as 4,000,000 cycles, is exemplified in Figure 10, and this frequency with the bridge unbalanced by a gauge under maximum stress is shown in Figure 11 wherein it varies from 4,000,000 to 4,005,000 due to the frequency modulation shown by the curve of Figure 9. The is exemplified by Figure 12. When the variable it produces an audio determined by the input fixed frequency of the oscillator 82 varies between its normal.

at 84 (Figure 3) which acting upon the gauge. This makes available for transmission to a recording mechanism variable frequencies of constant amplitude.

The invention in the form disclosed is applicable to advantage in recording flight and/or stress data on an aeroplane operating under conditions which cause very rapid changes in the gauges located about the plane. For example, it is possible to obtain accurate recordings during a dive, wherein the stresses may change from normal to maximum in a few seconds. The invention is equally applicable to the production of signals indicating changes in a plurality oi! stationary gauge devices when it is desirable to transmit them over a single line or transmitter to a remote point.

If a record is desired of the changes in a gauge at a single detection station it is possible to obtain a continuous record by stopping the switch mechanism 6i to connect in the desired gauge, or by adjusting the switch mechanism manually to select the desired gauge. With the apparatus of Figure 3 otherwise in operation, the transmitter 35 will then broadcast an audio frequency signal which varies in frequency proportionally to changes in the gauge and which is of constant amplitude. The transmission of this signal is continuous, with the result that a continuous record can be obtained.

Generally, in obtaining data on an aeroplane it is desirable to record the changes occurring at a considerable number of detection stations. The particular form of the invention illustrated provides contacts on the switch mechanism 6| to accommodate twenty-two gauges. In using a plurality of gauges it is also each gauge a substantially continuous record. This is possible with the invention herein disclosed because of the high speed operation it permits with accurate results.

The rotating switch arms 62 and 63 are, in the preferred form of the invention, driven by the motor 60 at a speed of approximately 250 R. P. M.

so that contact is made with all of the gauges each quarter second. Although the gauges are connected with the bridge circuit successively, the time for completing a cycle of operation is so small /4 second) that recordings are made from all the gauges substantially simultaneously. The switch arms and switch contacts may be of such arcuate widths as to provide contacts of approximately /io0 second duration. Recordings of such short duration are possible in part because of the large frequency swing (0 to 5000 cycles) provided by the appartaus for the audio frequency beat signals.

The gauges may be of various conventional types selected for the particular flight and physical stress characteristic under observation.

The gauges for detecting strains in various parts of the plane may, as shown in Figures and 16, comprise conventional wire wound unit-s 95 including an active portion 9'8 and an unstressed dummy portion 93 mounted on the same type of material, the active portion being responsive to the changes in strain of the associated part. The two portions of such a gauge are corrected into opposite arms of a Wheatstone bridge as illustrated in Figure 3, so as to compensate for any temperature changes, either in the gauges or in the leads to the gauges.

A gauge for recording changes in air speed, as shown in Figures 17 and 18, may consist of a reluctance type unit 99 having two coils I08 and lei for connection to the bridge circuit. This desirable to obtain for purpose of demonstrating the invention;

unit may have an armature I02 moving in relation to the two coils thereof and coupled to a conventional air speed diaphragm I03.

For recording acceleration it is possible to use a wire wound strain gauge, of the sort shown in Figures 15 and 16, actuated by a standard type of accelerometer. As shown in Figures 19 and 20, various types of resistance gauges may be employed for appropriate gauging purposes. For recording changes in angularity of elevators, rudders, flaps, and other relatively movable parts, a conventional potentiometer I04, as shown in Figure 19, may be linked to the elevator, rudder, flap, or other movable member, by drivingly connecting the movable arm I05 to the movable member, the movement of which is to be indicated, recorded, or otherwise gauged. In such an arrangement the potentiometer forms the two arms of the bridge circuit.

As indicated in Figure 20, temperatures, as, for example, oil temperature, or air temperature, may be indicated, recbrded, or otherwise gauged by means of a resistance type unit I06, responsive to the temperature to be measured, and connected in one of the arms of the bridge circuit; and it is obvious that numerous other conventional devices, adapted for employment in connection with sort illustrated in Figure 3, may be employed for gauging and applying any desired variable data upon the system forming the subject matter of the present invention.

In operating, the apparatus, when embodying a plurality of gauges, transmits in repeated and rapid sequence variable audio frequency signals which vary in accordance with the different gauges. As mentioned hereinbefore, these signals may be received in an apparatus as illustrated in Figure 2, then amplified, and recorded on a conventional 16 mm. film type sound recorder. Preferably, timing points are introduced into the signal by the switching device and are available for use in controlling the synchronizing of the film in a suitable power driven analyzer.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description; and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing its attendant advantages, the form herein disclosed being a. preferred embodiment for the and we do not herein claim the patentable combination embodying particular features of the receiver and recorder mechanism, or the manner of operating the same, as claimed in a co-pending application Serial No. 549,440; nor the combination including particular features of the recording apparatus and the operation thereof, the same being'claimed in a co-pending application Serial No. 549,441; nor the combination forming a. telemetric system including a plurality of sending stations and the means of operating the same, as claimed in a co-pending application Serial No. 549,442 (now Patent No. 2,446,803, dated April 12, 1949); nor the combination embodying specific means for accomplishing the frequency variation of signal impulses in repeated succession and the manner of so operating a telemetric system, as claimed in a co-pending application Serial No. 549,443 (now Patent No. 2,446,804, dated April 12, 1949); the

of the potentiometer Wheatstone bridge circuits of the present invention herein claimed residing in the combinations recited in the appended claims.

I claim:

1. An apparatus for ing changes in characteristics of remote gauges comprising, in combination, a plurality of gauge devices each acting when operated to vary an electrical property thereof, a bridge circuit having at least one leg thereof open for the connection of a gauge device thereto, means for producing a carrier wave therefor, a high speed switching device operable during continuous movement thereof. successively to connect said gauge devices individually into the bridge circuit to effect mod ulation of said carrier wave for short periods of time, means acting on the carrier so as to leave a potential changing in proportion to the changes in the gauge device then connected through the jected to said potential to vary the frequency of the oscillations produced thereby.

nals varying voltage. 4. In a system tially continuously from a plurality of detection producing signals indicatcuit including one of said devices at a time, means for producing a carrier wave therefor, means including a motor-driven switching device operable during continuous movement thereof successively to connect said bination,

producing including a high speed motor-driven switching device operable during continuous movement thereof successively to connect said gauge devices individually into said bridge circuit to effect means interconnected with said gauge devices and 9. Signalling apparatus comprising bridge means forming one side of an a carrier wave therefor, and means other side of said electrical bridge, means for applying alternating electrical potential across said bridge whereby to deliver therefrom a carrier wave modulated, during successive intervals, in accordance with the electrical characteristics of said gauge devices, and means for generating audio frequency signals varying, during successive intervals, in accordance with said modulated carrier wave.

10. Signalling apparatus comprising bridge means forming one side of an electrical bridge, a plurality of gauge devices, each comprising means having electrical characteristics that vary in response to variable conditions to be signalled, continuously and repeatingly rotatable switch means interconnected with said gauge devices and said bridge means for successively, rapidly and cyclically connecting said gauge devices to form the other side of said electrical bridge, means for applying alternating electrical potential across said bridge, whereby to deliver therefrom a carrier wave modulated, during successive intervals, in accordance with the electrical characteristics of said gauge devices, means for amplifying said REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,786,780 Shepard Dec. 30, 1930 1,849,827 Fitzgerald Mar. 15, 1932 1,849,870 Shepard Mar. 15, 1932 1,965,393 Schleicher July 3, 1934 2,210,970 Bonell Aug. 13, 1940 2,378,395 Dickson June 19, 1945 FOREIGN PATENTS Number Country Date 502,711 Great Britain Mar. 23,- 1939 

